Method and apparatus for cold drawing or rolling of metal wire rod

ABSTRACT

A method and apparatus for wire drawing using the oval-round series in which wire rod is fed through the round groove rolls in a manner such that axially directed forces having the same direction are imposed on both round groove rolls thereby preventing displacement of the rolls in opposite directions and stabilizing the wire rod in the round groove.

United States Patent [1 1 m1 3,811,309 Nordstrom May 21. I974 METHOD AND APPARATUS FOR COLD [56] References Cited DRAWING OR ROLLING OF METAL WIRE UNlTED STATES PATENTS ROD 3,564,891 2/1971 Norlindh 72/231 Inventor: Knut Lennart Nordstrom, l X sou-lemsvagenv Smedjebacken 2.105.258 1/]938 OMalley 72/227 Sweden 2140,414 l2/l938 Brownstein 72/235 Filed: p 8, 1972 Primary Examiner-Milton S. Mehr [21] App]. No.: 287,227

[57] ABSTRACT A method and apparatus for wire drawing using the [30] Forelgn Appllc ahon Pnomy Data oval-round series in which wire rod is fed through the Sept. 10, 1971 SWltZel'lZlfld round groove rolls in a manner Such rected forces having the same direction are imposed on both round groove rolls thereby preventing dis- 58] i 72/234 5 366 231 placement of the rolls in opposite directions and stabilizing the wire rod in the round groove. 6 Claims; 12 Drawing Figures PATENTEDmm m4 3.811.309

SHEET 8 OF 3 FIGZB FIG. 5

memmmm m4 3811 309 SHEET 3 0F 3 METHOD AND APPARATUS FOR COLD DRAWING OR ROLLING OF METAL WIRE ROD This invention relates to the art of wire drawing and, more particularly, to an improved method and apparatus for cold drawing or rolling of metal wire rod by utilizing the oval-round reduction series.

A reduction series very often used in wire drawing is the oval-round series in which the wire rod is first formed in a pair of rolls to oval cross section and, immediately thereafter, in subsequent roll pairs is formed to a given round cross section. With such an arrangement, the round groove rolls normally are positioned in a plane which is at an angle of 90 relative to the plane of the oval groove rolls, the reason for this being that it eliminates the necessity of turning the oval shaped wire through 90, as is sometimes done in hot rolling and which requires substantial guide equipment.

The above described method of wire reduction is applied practically exclusively where wire rod drawing is accomplished with roller dies, that is, where the drawing die is replaced by a roller die unit. The term roller die" unit refers to a set of nondriven rolls of which the first roll pair, in the drawing direction, has oval grooves and the second roll pair has round grooves. The two roll pairs are set at an angle of 90 relative to each other but the center line of the roll path defined by the two roll pairs are aligned and coaxial.

. One problem with the above-described arrangement is the instability of the oval wire rod as it enters the round groove rolls. This instability results from the play inherently present in the bearings and mountings of the round groove rolls. Due to the presence of this play, the oval wire rod entering the grooves will frequently impose forces on the rolls which will displace one roll relative to the other in opposite axial directions. The' result of this displacement of the rolls isa wire rod that is more oval than round in cross sectional configuration.

While this problem can be alleviated, to some extent, by placing holders between the oval groove rolls and the round groove rolls, this solution has the disadvantage that the holder can scratch the wire rod unless it is provided with rollers which, in turn, complicates the construction. In any event, the holders do not entirely eliminate the instability of the oval wire rod as it enters the round groove rolls.

Another theoretically possible solution to this problem is to preset the round groove rolls in an axially offset manner such that the oval wire rod will coact with the round rolls to return the rolls totheir proper position. However, this solution is no more than theoretical since the instability of the oval wire rod renders it impossible to predict the direction in which the forces will be imposed on the round rolls. As a result it is entirely possible that the oval wire rod will impose axial forces on the round rolls in the same direction as the rolls are preset, thereby aggravating rather than solving in opposite directions and assuring that a round wire is produced.

A more complete understanding of the invention will be received from a complete reading of the following description which, together with the attached drawings, discloses but certain formsof the preferred embodiment of the invention.

Referring now to the drawings wherein like reference numerals indicate like parts in the various views:

FIG. 1 is a schematic illustration of a conventional prior art cold wire drawing process;

FIG. la is a view taken along line la-la of FIG. I;

FIG. 1b is a view taken along line lb--Ib of FIG. 1;

FIGS. 2A-D are schematic graphic presentations of the problem solved by the instant invention;

FIG. 3 is a diagrammatic illustration of the displacement of the rolls relative to each other which takes place with the prior art arrangement;

FIG. 4 is a schematic illustration of one embodiment of the invention;

FIG. 4a is a view along line 4a4a of FIG. 4;

FIG. 4b is a view along line 4h4b of FIG. 4;

FIG. 5 is a schematic presentation of the cold wire drawing process and-the forces created using the solution of FIG. 4.

Referring now more in detail to the drawings, FIG. 1 illustrates a conventional roller die" unit used in an oval-round series and comprises one roll pair I, 2 defining an oval groove 6 and a second roll pair 3, 4 defining a round groove 7 Roll pair 3, 4 lie in a plane that is rotated by 90 from the plane of the roll pair 1, 2 (see FIG. 1B). The wire rod to be drawn is designated by the numeral 5. Subsequentto its forming to oval section,

the wire rod is designated at 5' and subsequent to its forming to a round shape is designated at 5". FIG. 1B

shows in detail how the oval and round grooves are shaped relative to each other and, as is apparent from that Figure, the center line of the roll paths through both the oval and round grooves are in alignment and coaxial. v

FIGS. 2A-D illustrate the problem solved by this invention. FIG. 2A presents the desired theoretical relationship between the round groove 7 and the oval wire rod 5 as it enters the round groove. In this orientation, the major axis of the oval cross section lies in a plane which is perpendicular to the axis of each of the rolls 3 and 4.

FIGS. 28 and 2C illustrate the problem which occurs when the oval wire rod 5' enters the round groove 7 in I an unstable condition. For example, FIG. 2B shows the rolls 3, 4 as being axially displaced in opposite directions which results from the oval wire rod being slightly inclined to the right as viewed in FIG. 28. FIG. 2C illustrates how the two rolls 3, 4 are axially offset in the opposite 7 direction when the oval wire rod. enters the groove 7 inclined to the left, as viewed in that Figure.

FIG. 2D schematically presents the forces that act on I.

the rolls 3, 4 to cause axial displacement of the rolls in the manner shown in FIG. 2B. As the wire rod isintroduced into the round groove rolls, the oval wire rod is subjected to a rolling pressure P,. due to the height of the rod exceeding the depth of the groove 7. Where the wire rod is inclined such that its major axis is no longer perpendicular to the axis of the rolls, the wire rod is subjected to a torsional movement M,.. The moment of reaction of the wire rod consists of a torsional resistance in the wire rod and axial forces P acting on the rolls 3, 4. As a result, the rolls 3, 4 will move axially in opposite directions until the play has been eliminated and the wire rod will then achieve a state of balance in which the moment of the axial forces P,, r and the torsional moment neutralize the moment caused by the rolling force P...

The inclined position of the oval wire rod and the resultant displacement of the rolls 3, 4 then produce in the final drawn product a wire rod having an ovality corresponding to FIG. 28. It will be appreciated that should the oval wire rod be inclined in the opposite direction to that illustrated in FIG. 2D, the same force analysis applies but the rolls 3, 4 will be offset in the opposite direction in the manner shown in FIG. 2C.

The magnitude of the axial displacement of each roll depends on the play that is present in the bearings and mountings and. further; on the elasticity of the material. FIG. 3 is a graphical presentation of these factors wherein the portion above the abscissa represents the upper roll and the portion below the abscissa represents the lower roll. The movement in axial direction which any pointfof any of the rolls can be displaced has been plotted along the abscissa. The points a and h indicate the total play in each direction as a function of the construction of the bearings and mountings. The elasticity ofthe material, as a function of the forces P has been superposed on points a and b with the total displacement, for a given force P appearing from the points c and d.

This invention proposes to solve the foregoing problem in themanner illustrated in FlG. 4. Thus, the roll pairs 1, 2 and 3, 4 are arranged such that the rolls 3, 4 are offset from the roll path through rolls 1, 2 by a distance A. Oval wire rod 5 fed through rolls 3, 4 creates forces 8 which act on the two rolls in the direction indicated in H0. 4. The magnitude of the axial forces 8 is a function of the tensile stress P prevailing in the wirerod 5' between the roll pairs 1, 2 and 3, 4 and the incli nation a of the wire rod to the normal rolling path between the roll pairs. The magnitude of this force will be substantially smaller than the axial component of P,.. See FIGS. 2D and 4.

The play and the elasticity in the axial bearings and mountings of the two round groove rolls being equal,

the axial displacement of the rolls will be equal and in the same direction with the position of the round grooves relative to each other thereby remaining unchanged. T

. FIG. 4A shows a section along the line A-A in FIG. 4 and illustrates how-the oval wire rod 5 enters the round groove 7.

FIG. 4B shows a section along the line BB in FIG. 4 and illustrates the displacement of the oval groove rolls in relation tothe round groove rolls.

In view of the foregoing, it will be seen that the reaction forces of the round groove rolls acting on the oval wire rod. i.e.. the forces P,, in FIG. 5, will havea stabilizing effect to establish and maintain the ideal position of the oval wire rod in the round groove. i.e. 90 to the round groove rolls. A correction to compensate for the axial spring actions need not be made, and the wire rod is free of torsional stresses. Moreover, the axial forces which arise as a result of this method are substantially smaller than those encountered as a function of the roll pressure according to FIG. 2D. This is a great advantage from the standpoint of the life of the axial bearings of the rolls. I

It will be appreciated that either roll pair may be offset from the other to achieve the relationship shown in FIG. 4. However, the same end result may be obtained by maintaining the normal coaxial roll path and instead of shifting roll pairs, forcing the wire rod in a lateral direction by means of guide rollers. Such rollers may be placed between the roll pairs as well as after the round groove rolls, the essential point being that the wire rod acts on the round groove rolls to subject them to forces having the same direction.

While the invention has been described with reference to certain specific embodiments, neither the illustrated embodiments nor the terminology employed in describing them is intended'to be limiting; rather it is intended to be limited only by the scope of the appended claims.

Having described the invention, what is claimed is:

l. A method of establishing and maintaining a stable and correct position of metal wire rod having an oval cross section in a round groove during cold rolling or drawing with a roller die unit which includes a pair of oval groove rolls and a pair of round groove rolls, said method comprising the step of feeding the wire rod through the round groove rolls at an angle to the centerline of the roll path through the rolls to cause the wire rod to impose axial forces on each of the rolls with the axial forces acting in the same direction.

2. The method of claim 1 wherein the wire rod is fed into the round groove rolls at an angle of up to about 10 to the center line of the roll path through the rolls.

3. The method of claim 1 wherein the wire rod is fed from the round groove rolls at an angle of up to about 10 to the center line of theroll path through the rolls.

4. The method of claim 1 wherein the roll path through the pairs of rolls is aligned and coaxial and the step of feeding includes the steps of displacing the wire rod laterally of the roll path as it exits from the oval groove rolls, and

redirecting the wire rod to enter the round groove rolls at an angle of up to about 10 to the roll path.

5. Apparatus for cold rolling or drawing of metal wire rod including a roller die unit comprising a pair of oval groove rolls for shaping the wire rod to an oval cross section and a pair of round groove rolls for shaping the oval wire rod to a round cross section, the improvement comprising one of said pair of rolls being offset in the axial direction of said round groove rolls relative to the other pair of rolls whereby the oval wire rodenters said round groove rolls at an angle to the roll path and imposes axial forces acting in the same direction on said round groove rolls.

6. The apparatus of claim 5 wherein said angle is up to about 10.

V UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3 r8 1- I v Dated May' 21 19 74- Inventor-(s) Knut I L Nordstrom It is certified that error appears in the above-identified patent and. that said Letters :Patent are hereby corrected as shown below:

i In the foreigh application priority data, chaage "Sept, 10, I i l il Switzerland 11 495/71" to read -=-Sept. 10, 1am. sweaenv i. 11495/71--. A

Signed and sealed this 22nd day of October 1974.,

(SEAL) Attest:

MCCOY M. GIBSON .JR.

c. MARSHALL DANN Attest1ng-Officer Commissioner of Patents F ORM P04 050 (10-69) USCOMM-DC 50376-P69 fi' U.S, GOVERNMENT PRINTING OFFICE $969 O-365336, 

1. A method of establishing and maintaining a stable and correct position of metal wire rod having an oval cross section in a round groove during cold rolling or drawing with a roller die unit which includes a pair of oval groove rolls and a pair of round groove rolls, said method comprising the step of feeding the wire rod through the round groove rolls at an angle to the centerline of the roll path through the rolls to cause the wire rod to impose axial forces on each of the rolls with the axial forces acting in the same direction.
 2. The method of claim 1 wherein the wire rod is fed into the round groove rolls at an angle of up to about 10* to the center line of the roll path through the rolls.
 3. The method of claim 1 wherein the wire rod is fed from the round groove rolls at an angle of up to about 10* to the center line of the roll path through the rolls.
 4. The method of claim 1 wherein the roll path through the pairs of rolls is aligned and coaxial and the step of feeding includes the steps of displacing the wire rod laterally of the roll path as it exits from the oval groove rolls, and redirecting the wire rod to enter the round groove rolls at an angle of up to about 10* to the roll path.
 5. Apparatus for cold rolling or drawing of metal wire rod including a roller die unit comprising a pair of oval groove rolls for shaping the wire rod to an oval cross section and a pair of round groove rolls for shaping the oval wire rod to a round cross section, the improvement comprising one of said pair of rolls being offset in the axial direction of said round groove rolls relative to the other pair of rolls whereby the oval wire rod enters said round groove rolls at an angle to the roll path and imposes axial forces acting in the same direction on said round groove rolls.
 6. The apparatus of claim 5 wherein said angle is up to about 10*. 